1. Field of the Invention
The present invention relates to a thermal processing apparatus that performs thermal processing of a semiconductor wafer and a glass substrate, etc. (hereinafter referred to simply as a “substrate”) by irradiating flashlight to the substrate.
2. Description of the Background Art
In an ion activation step of a semiconductor wafer after being subjected to ion implantation, there has heretofore been employed a thermal processing apparatus such as a lamp annealing apparatus using halogen lamps. In such a thermal processing apparatus, the ion activation of a semiconductor wafer is carried out by heating (annealing) the semiconductor wafer to temperatures of, for example, approximately 1000° C. to 1100° C. This thermal processing apparatus is configured so as to elevate the temperature of the substrate at a speed of about several hundreds of degrees per second, by utilizing the energy of light irradiated from the halogen lamps.
Japanese Patent Application Laid-Open No. 2000-223547 discloses this type of lamp annealing apparatus. In this apparatus, thermal processing is performed within a chamber in which a large number of halogen lamps that are usually point light sources are arranged, and a transport robot loads and unloads a substrate with respect to the chamber. Japanese Patent Application Laid-Open No. 9-263939 (1997) discloses a thermal processing apparatus using a tubular infrared lamp heater, in which the direction of substrate transport by a guided vehicle is set parallel to the, longitudinal direction of the infrared lamp heater.
However, even when the ion activation of a semiconductor wafer is executed by using a thermal processing apparatus that elevates the temperature of a substrate at a speed of about several hundreds of degrees per second, the profile of ions implanted into the semiconductor wafer becomes round. That is, it has been found to cause the phenomenon that ions diffuse by heat. In the event that this phenomenon occurs, even if ions are implanted at a high concentration into the semiconductor wafer surface, the implanted ions may diffuse. This introduces the problem that it is necessary to implant more ions than necessary.
In order to solve the above problem, for example, Japanese Patent Application Laid-Open Nos. 59-169125 (1984) and 63-166219 (1988) have proposed a technique of elevating only the temperature of the surface of a semiconductor wafer after being subjected to ion implantation in an extremely short period of time (not exceeding several milliseconds) by irradiating flashlight to the surface of the semiconductor wafer by use of xenon flash lamps, etc. Under the temperature elevation in a very short time by the xenon flash lamps, the ions will not have a sufficient time to diffuse. It is therefore possible to execute only the ion activation, without rounding the profile of ions implanted into the wafer.
However, although the infrared lamp heater exerts uniform output characteristics in the longitudinal direction, the xenon flash lamps, the luminous principle of which is completely different, cannot exert uniform output characteristics in the longitudinal direction. That is, in the xenon flash lamp a predetermined luminous intensity is obtainable only in a portion in the vicinity of the center. For this reason, in order to ensure the necessary effective irradiation region, it is unavoidable to use xenon flash lamps of considerable length. This might enlarge the overall size of the thermal processing apparatus.
Since processing apparatuses for semiconductor wafers and the like are usually disposed in a clean room, the increased size of the apparatus is a problem. In order to improve the production efficiency of a processing apparatus, it is also important that the processing apparatus is excellent in maintainability.